SLC18B1 encodes a vesicular polyamine transporter (VPAT) that mediates proton-coupled transport of polyamines into secretory vesicles 1. The protein functions as an antiporter, coupling H+ efflux with polyamine (spermine and spermidine) uptake using the electrochemical gradient established by V-ATPase 2. SLC18B1 is the fourth member of the SLC18 transporter family, which includes vesicular monoamine and acetylcholine transporters 3. In neurons and astrocytes, SLC18B1 mediates vesicular storage and exocytotic release of polyamines, which function as neuromodulators at ionotropic receptors, particularly N-methyl-D-aspartate receptors 2. SLC18B1 knockout in mice decreased brain polyamine levels by ~20% and impaired both short- and long-term memory 1. In mast cells, SLC18B1 regulates polyamine accumulation in secretory granules, potentiating degranulation and histamine secretion 1. The transporter is also expressed in megakaryoblastic cells and platelets, where it mediates stimulus-dependent polyamine release 4. Genetically, SLC18B1 variants, including missense variant rs41286192, are associated with shared genetic architecture linking metabolic dysfunction and neurodegenerative diseases through neurotransmitter transport mechanisms 5. These findings establish SLC18B1 as a critical regulator of polyamine-mediated chemical transmission with implications for neurological and immune function.